This invention applies to rotating joints or unions connected to a rotating element wherein fluid is passed through the joint to the rotating element. More particularly, to rotating joints used to conduct fluids with lubricating capacity to rotating elements.
Rotary unions are used in apparatus to introduce a viscous substance into a rotating element, for example, in expandable shaft systems. The functional assignment of rotary union in expandable shaft systems is typical of other systems employing rotary unions. Expandable shafts are generally designed such that cutting elements carried by the shaft are secured in place when a fluid is conducted into the shaft under pressure, thereby causing the shaft to expand, locking the elements in place. As the expandable shaft is rotated, a material usually in sheet form, for example, corrugated board, is passed over the shaft, whereupon the cutting elements cut the material. Rotary unions are used in expandable shaft systems as a means by which pressure influenced fluid is admitted to the shaft. The shaft expansion is very slight, therefore, the rotary union must be able to maintain a constant feed such that the pressure can be continuously monitored and adjusted to compensate for any system leakage which may occur while the shaft is rotating.
Rotary unions generally employ a housing which defines a cylindrical chamber and a rotatable shaft, rotatably mounted within the chamber. The rotating shaft is designed to receive and conduct fluids to a rotating element which is suitably attached to the rotating shaft. Rotary unions are usually an integral component in a system or sub-system. Therefore, the necessity of repairing or replacing the rotary union will require system shutdown resulting in the loss of system productivity. The primary cause of rotary union failure is wearing of union internal elements due to the presence of several moving elements within the union, for example, bearings and sealing rings. Generally, the more moving elements a component or apparatus has, the more susceptible the apparatus to wear failure, especially when the elements are subjected to high speed motion for prolonged periods of time. Rotary unions are extremely vulnerable to wear, especially when deployed in high speed industrial machinery. A complementary factor in the promotion of wear is the presence of heat. Available rotary unions provide no means by which heat due to friction can be dissipated.
The presence of a lubricant acts to minimize wear; however, under extreme operating conditions such as those existing in industry, the prolonged exposure of a lubricant to heat (friction-generated heat in the case of the rotary unions) causes the lubricant to first thin and then decompose. As a result of lubricant decomposition, unions must receive frequent replenishment of lubricant which requires system shutdown resulting in loss of system productivity.
The present invention provides a rotary union with a longer operating life during which minimum servicing is required.